[M T]

Looking at the 200 relay prelim, why weren't TAMU and NC State dq'ed for leaving early?  Both seem to have early departures in the transition between back and breaststroke - TAMU -0.86 and NCSt -0.70.  That's a of exceedingly large proportions advantage in a race where all 8 teams were with a second.

In the 400 medley relay final, the Stanford breaststroker's reaction time was -0.62.  This can happen if the backstroker's touch isn't recorded by the touchpad.  You already mentioned the video review.  An early start of that magnitude would have been obvious (at 2 yards/second, that's about 1.5 yards or so).

This is a picture of the early start by Cal in the 400MR final (not sufficient to call a DQ, but shows the magnitude of the jump).  You can see the Stanford swimmer Lia Neal in the background.  The Stanford swimmer (unseen, in the water) touched 0.02 before the Cal swimmer.  Lia's reaction time was 0.26 (about normal, but a bit slow), meaning the sensor felt her push off the block 0.26 seconds after the previous swimmer touched.  The Cal swimmer's reaction time was recorded as -0.13.

While it is understandable to me that a backstroker's touch might not get recorded, I also saw a relay in which the butterflyer's touch wasn't recorded.  (Not recorded probably means that there is enough noise in the signal from the sensor to decide what was a touch and what wasn't.)  That's much more surprising to me, but I haven't looked at the performance of these touchpads.  My impression of touchpads from years ago was that they required a direct, firm hit to record, while brushing the pad didn't get recorded.  I'm sure they've tweaked the sensitivity to allow lighter touches, but then noise (from waves) could possibly be a problem.

[M T]

Looking at the 200 relay prelim, why weren't TAMU and NC State dq'ed for leaving early?  Both seem to have early departures in the transition between back and breaststroke - TAMU -0.86 and NCSt -0.70.  That's a of exceedingly large proportions advantage in a race where all 8 teams were with a second.

In the 400 medley relay final, the Stanford breaststroker's reaction time was -0.62.  This can happen if the backstroker's touch isn't recorded by the touchpad.  You already mentioned the video review.  An early start of that magnitude would have been obvious (at 2 yards/second, that's about 1.5 yards or so).

This is a picture of the early start by Cal in the 400MR final (not sufficient to call a DQ, but shows the magnitude of the jump).  You can see the Stanford swimmer Lia Neal in the background.  The Stanford swimmer (unseen, in the water) touched 0.02 before the Cal swimmer.  Lia's reaction time was 0.26 (about normal, but a bit slow), meaning the sensor felt her push off the block 0.26 seconds after the previous swimmer touched.  The Cal swimmer's reaction time was recorded as -0.13.

While it is understandable to me that a backstroker's touch might not get recorded, I also saw a relay in which the butterflyer's touch wasn't recorded.  (Not recorded probably means that there is enough noise in the signal from the sensor to decide what was a touch and what wasn't.)  That's much more surprising to me, but I haven't looked at the performance of these touchpads.  My impression of touchpads from years ago was that they required a direct, firm hit to record, while brushing the pad didn't get recorded.  I'm sure they've tweaked the sensitivity to allow lighter touches, but then noise (from waves) could possibly be a problem.